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A cubic whose roots are permuted

Paper 2 · Algebra · Standard · 20 marks

The cubic equation  is denoted by (∗)(*).

  1. (i)
    Show that (∗)(*) has three real roots α\alpha, β\beta, γ\gamma with  , and  .
    4 marks
  2. (ii)
    Find the cubic equation whose roots are 1α\frac{1}{\alpha}, 1β\frac{1}{\beta}, 1γ\frac{1}{\gamma}, and the cubic equation whose roots are 1−α1-\alpha, 1−β1-\beta, 1−γ1-\gamma. Deduce that the sets {1α,1β,1γ}\left\{\frac{1}{\alpha}, \frac{1}{\beta}, \frac{1}{\gamma}\right\} and  are equal.
    5 marks
  3. (iii)
    Let  . Show that S(α)S(\alpha), S(β)S(\beta) and S(γ)S(\gamma) are roots of (∗)(*), and deduce that  , and  .
    5 marks
  4. (iv)
    Find the value of .
    6 marks

Every topic on both papers

Section A: Pure Mathematics

Algebra, Series, Curves, Integration, Trigonometry, Complex numbers, Vectors, Proof, Hyperbolics and polars, Differential equations

Section B: Mechanics

Forces, Energy and collisions

Section C: Probability and Statistics

Probability, Continuous distributions

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  • 96 problems
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